The present invention relates to a pulse coded railroad signaling system and, more particularly, to a scheme for efficiently incorporating a binary data capability into the system by utilizing the same medium of transmission without interfering with the operation of the signaling system.
Prior to this invention, railroads generally had no remote access to data at nodes other than Control Points. If it was desired by a railroad to have access to maintenance-related information at every node in a pulse coded signaling system, the railroad would have to install telephone lines or data radios at every node to relay this information back to the control office. This would be prohibitively expensive for most railroads. In fact, the development of pulse coded signaling systems using the rails as a transmission medium occurred precisely to enable the railroad to eliminate the costly wires previously run to every signaling node (also known as a xe2x80x98pole-linexe2x80x99) to carry vital signaling information.
In the present context, binary data transmission is defined as the transmission of messages composed of multiple binary data bits, where a binary data bit is the smallest quantum of information, having a value of 0 or 1. It will be helpful to describe current pulse coded railroad signaling systems to provide a background for understanding the invention. Current pulse coded railroad signaling systems convey vital (fail-safe) and non-vital signaling information through the rails from each end of a control block (called Control Points) to each node of the signaling system in the block. The block is defined to be a distance of railroad track (often many miles) which is terminated on each end by a Control Point and divided into a number of track circuits. A track circuit is defined as a section of railroad track that is electrically isolated from the other adjacent sections of track. Electronic equipment connects to each end of a given track circuit and, with the equipment at each end acting alternately as transmitter and receiver, uses the track as a communications medium to transmit information. An example of this type of electronic equipment is the ALSTOM Genrakode(trademark) product line. The vital and non-vital information transmitted through the track circuits is used to control wayside signals and for other control functions. The term node is used to describe a single instance of this electronic equipment that may communicate with one or two track circuits depending on the location of the nodes in the block. The nodes at each end of the block (Control Points) need only communicate with one track circuit whereas the other nodes (Intermediates, Repeaters, and Switch Locks) generally communicate with the two track circuits on either side of a track circuit boundary.
Control Points are so named because they are the nodes with direct communications links to the central control office for control of train routing. Intermediates are nodes that drive intermediate signals to control train movements. Repeaters are used where track circuit length between other nodes is too great and it is necessary to bridge the distance between two nodes. Switch Locks are used to electrically control access to a hand-throw track switch mechanism in a fail-safe manner. Communications between each adjacent node occurs on a nominal 2.8 second cycle time (although other cycle times may be used). Each node is a transceiver, which transmits for half of the cycle and receives for the other half of the cycle. The conventional vital signaling information is not binary. The data in each cycle can be one of several values (termed codes) as opposed to only two values (0 or 1). The codes are decoded and used by the system on a cycle-by-cycle basis. This type of system performs no encoding/decoding of data over multiple cycles, with the one exception being the Alternating Code 5 mode which uses data from two consecutive cycles for decoding.
The signaling information is represented by a limited number of codes, only one (two in special cases) of which is encoded per cycle. Each node can only receive codes from adjacent nodes (which are typically located 1-3 miles apart). Therefore, as shown in FIG. 1, Node 1 is only receiving codes transmitted directly from Node 2. This is adequate for operation of the signaling system; however, it would also be desirable to have the capability to transmit specific information from a node to any other node in the block. A specific example of this would be the capability to transmit maintenance-related information such as a burned-out signal bulb from the Wayside Signal location at Node 3 to Control Point A (Node 1), so this specific information may be passed on to the central control office. With this information, the control office can alert maintenance personnel to the exact location and nature of a problem to allow immediate corrective action to be taken to minimize or prevent train delays.
Accordingly, a primary object of the present invention is to enable an efficiently operating scheme to report on maintenance and other problems over a common railway signaling transmission means.
The present invention conveys maintenance-related data (or any other non-vital information) to from any node using the same transmission medium (the rails) as the pulse coded vital signaling. This data can therefore be sent to the Control Points where a communication link to the central control office already exists. Since this new communication capability takes advantage of an existing transmission medium and existing hardware (the current signaling system), the cost to utilize this new capability is minimal.
This invention provides the above-noted capability by overlaying a binary data protocol on the existing pulse coding scheme to send binary data from any node in the block to any other node, and thence to a control point, while not interfering with the existing operation of the signaling system.
The invention can be used in commercial applications to transmit specific information from any one node to any other node in a pulse coded railroad signaling system, which is not currently possible. The most obvious example of this (cited as an example in the previous section) is maintenance-related information.
The foregoing and still further objects and advantages of the present invention will be more apparent from the following detailed explanation of the preferred embodiments of the invention in connection with the accompanying drawing.